demo_nodes_cpp_native
C++ nodes which access the native handles of the rmw implementation.
README
What Is This?
This demo provides an example of further Quality-Of-Service (QoS) configurability as well as Publication Modes in a ROS 2 node via the use of rmw_fastrtps_cpp Application Programming Interface (API).
The example utilitises eprosima::fastdds::statistics::dds::DomainParticipant as well as eprosima::fastdds::dds::DataWriter.
A DomainParticipant defines a singular working unit which groups a set of Publishers and Subscribers together. See References - DomainParticipant for more details.
A DataWriter is created by a Publisher and writes data to a topic with configurable behaviors. See References - DataWriter for more details.
Build
colcon build --packages-up-to demo_nodes_cpp_native
Run
ros2 run demo_nodes_cpp_native talker
Verify
When executed correctly, the following strings should be printed to the terminal similar to what is shown below:
[INFO] [1674525877.083735645] [talker_native]: eprosima::fastdds::dds::DomainParticipant * 94193367466752
[INFO] [1674525877.084105822] [talker_native]: eprosima::fastdds::dds::DataWriter * 94193370040688
[INFO] [1674525877.584006930] [talker_native]: Publishing: 'Hello World: 1'
[INFO] [1674525878.083967966] [talker_native]: Publishing: 'Hello World: 2'
[INFO] [1674525878.583917242] [talker_native]: Publishing: 'Hello World: 3'
[INFO] [1674525879.083963276] [talker_native]: Publishing: 'Hello World: 4'
[INFO] [1674525879.583918839] [talker_native]: Publishing: 'Hello World: 5'
#...
FAQ
Q: Why use rmw_fastrtps_cpp API directly?
A: ROS 2 only allows for the configuration of certain middleware QoS (see ROS 2 QoS policies). In addition to ROS 2 QoS policies, rmw_fastrtps sets two more Fast DDS configurable parameters:
History memory policy:
PREALLOCATED_WITH_REALLOC_MEMORY_MODE
Publication mode:
ASYNCHRONOUS_PUBLISH_MODE
In addition, rmw_fastrtps offers the possibility to further configure Fast DDS:
Q: Is it still called Fast RTPS?
A: No. Fast RTPS has been renamed to Fast DDS since ROS 2 Foxy.